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trol of postharvest bud necrosis in oriental hybrid lilies

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					                                                                                                       no. July 07




                                           This Flower Bulb Research Program Newsletter is published by Anthos,
                                           Royal Trade Association for Nurserystock and Flowerbulbs in coopera-
                                           tion with Dr. Bill Miller of Cornell University.



Causes and Control of Cold-Storage-Induced                thos) looking into the causes, development and con-
Bud Necrosis in ‘Mona Lisa’ Lilies                        trol of postharvest bud necrosis in oriental hybrid
                                                          lilies.
Hye-Ji Kim and William B. Miller
Cornell University                                        What We Did
                                                          We grew ‘Mona Lisa’ lilies in a glass greenhouse
Oriental hybrid lilies are an important crop in the       maintained at 17C under natural sunlight with a
international floriculture industry with a wholesale      standard fertilizer regime and moved them to va-
value of more than $65 million in the U.S alone.          rious growing temperatures (17C, 21C, or 26C) and
When crops are finished earlier than market de-           light conditions (full sun, 25%, 55% or 85% light
mands, cold storage is often inevitable before mar-       reduction from black shading cloth) about a week
keting. Common disorders associated with cold             before cold storage. At the puffy bud stage (the
storage of potted hybrid lilies are accelerated leaf      most mature bud of the inflorescence showing full
yellowing, flower abscission, and bud abortion.           color, but not open), they were moved to 3C or 7C
While the leaf yellowing problem has been substan-        dark cold storage, or to 7C for two days, followed by
tially solved by the registration and use of Fascinati-   3C. Plants were held in cold storage for 2 weeks to
on (a gibberellin and cytokinin-containing product        observe how bud necrosis develops. We were able
from Valent USA), in recent years we have heard           to develop a rating system to indicate the amount of
increasing reports from growers about a new cold-         visual injury to the buds (Fig. 3). Bud size was mea-
storage problem in Oriental hybrid lilies. Since the      sured before and during cold storage.
disorder is characterized by sunken, darkened or
brownish areas on unopened buds (Fig. 1), we have         When does bud necrosis develop?
adopted the term ‘bud necrosis’ to describe it. Ba-       Susceptible plants develop initial symptoms within a
sed on comments from growers, bud necrosis is             day or two in cold storage (3C). Symptoms gradu-
most common when plants are finished in hot sum-          ally increase over the first week in the cold storage,
mer periods then placed directly in cold storage.         but stops in the second week. Thus, if an individual
‘Mona Lisa’ (Fig. 2) is a particularly susceptible cul-   bud does not develop bud necrosis in the first week
tivar, but many other pot and cut cultivars are also      of cold storage, it will not become necrotic during
susceptible.                                              the rest of storage period. Therefore, it is important
                                                          to control the development of bud necrosis during
While bud necrosis occurs in storage, we were inte-       the first couple of days in cold storage.
rested in whether greenhouse growing conditions
(for example, heat or intense light or possibly both)     Factors affecting bud necrosis
play a role in bud necrosis, or whether the sudden        1. Bud size Bud size at the time of cold storage is an
temperature drop from the greenhouse to the cold          important factor for susceptibility to bud necrosis.
storage is responsible. Therefore, we manipulated         In ‘Mona Lisa’, light green- to white-colored-buds,
growing temperature, light intensity, and cold stora-     5 to 10 cm long, are the most susceptible, while buds
ge temperature to figure out the causes of bud necro-     smaller (green buds less than 5 cm long) or larger
sis problem. The following is a summary of Cornell        (fully developed puffy buds) than this are not affec-
research (generously supported by Group 1 of An-          ted. Fig. 4 shows various sizes of buds along the flo-


                                                                                  Research Newsletter July 2007 pagina 1
wer stem. Completely green upper buds or lower           perature (26C) just for one week (at the end of for-
buds at the puffy bud stage or at fully developed        cing) induced severe bud necrosis in the cooler, as
white-colored-bud stage don’t get bud necrosis. It is    shown in Table 1.
the intermediate-sized buds that are at risk of deve-
loping bud necrosis.                                      4. Sudden temperature drop in cold storage Buds of
                                                         ‘Mona Lisa’ lily will get bud necrosis when directly
At the end of normal forcing, the intermediate-sized     moved to a 3C cold storage even if they are grown at
buds happen to be in the middle of the inflorescence,    a greenhouse temperature (17C) that does not encou-
so it was an open question as to whether bud positi-     rage bud necrosis. It seems possible that the sudden
on on the stem was also a casual factor. Therefore,      temperature drop from the greenhouse to a cold
we ran a series of experiments with different bulb       storage causes a temperature shock, especially on
sizes and suppliers. The results indicated that re-      the most susceptible, actively growing buds.
gardless of the number of buds on the stem or bud
position (top, middle, bottom), buds size ranging        Based on our findings, bud size, greenhouse tempe-
from 5 to 10 cm are in fact the most sensitive to bud    rature and light level and cold storage temperature
necrosis. The position of the bud along the stem is      all interact to induce bud necrosis during cold stora-
not important.                                           ge. Each of these factors is important. When sus-
                                                         ceptible cultivars are grown under both intense light
We measured the change in bud size over time du-         and high temperature, and moved directly to low
ring cold storage to find out why certain size classes   temperature cold storage, bud necrosis can be severe
of buds are more susceptible. Our results show that      and cause serious economic loss! Now that we have
the buds at high risk of getting bud necrosis are mo-    basic information on the causes of bud necrosis, we
re actively growing right before and after cold stora-   can suggest solutions to prevent the problem.
ge compared to smaller or larger buds. Therefore, if
they are moved to a cold storage while they are in a     How can we prevent bud necrosis?
“growing mode”, their growth may be disturbed and        1. Reduce light intensity during production Putting
necrotic spots or areas are generated on those active-   up a heavy shade cloth (85%) at least one week be-
ly growing region, such as bud tip or tepal fringes.     fore finishing the crops will reduce the incidence of
The greenhouse cultural practices we have found          bud necrosis. In one experiment, lilies that received
effective in reducing bud necrosis (reduced tempera-     shade only in the last 3-4 days all got bud necrosis
ture and light) also act to reduce bud growth rate.      regardless of shade level or cold storage temperatu-
                                                         re. Therefore, the shade duration at finishing should
2. Light intensity High light intensity is also an im-   be longer than a week.
portant factor for bud necrosis. For this research, we
grew ‘Mona Lisa’ lilies over many months, so we          It would be also possible to reduce greenhouse tem-
set up high (26C) temperatures and supplemental          perature to a lower level (optimally 17C) for the last
lights to simulate hot summer days. The basic light      week of forcing, then gradually reduce temperature
intensity was approximately 600 uM.m-2.s-1, and          after plants are in cold storage. If the facility has
we gave 0%, 25%, 55% or 85% shade cloth about a          automated shade cloth, however, this might be the
week before cold storage. As shown in Table 1, high      easiest option depending on outside temperatures.
light increased the incidence of bud necrosis (despite
cold storage temperature), and shade reduced it.         A warning: some lily cultivars are susceptible to flo-
                                                         wer abortion from low light, and this must be evalu-
3. High growing temperature To test the effect of        ated on a case-by-case basis.
growing temperature, we moved plants to a 26C
greenhouse (without supplementary lighting) about a      2. Gradually reduce temperatures in cold storage If
week before cold storage. Exposure to a high tem-        feasible, we recommend to initially store susceptible


                                                                                 Research Newsletter July 2007 pagina 2
lilies at 7C for two days, then reduce the temperature
to 3C after 2 days. While this staged temperature
reduction is not for reducing bud necrosis, as shown
in Fig. 4, buds continue development at the warmer
temperature, and may even bloom, becoming unmar-
ketable. Therefore, for longer storage, it is impor-
tant to bring the cold storage temperature down to
3C after two days at 7C. To avoid leaf yellowing, a
Fascination treatment should be applied before cold
storage.

3. What about a chemical remedy?                 DPA     Fig. 1. Bud necrosis on ‘Mona Lisa’ lilies.
(diphenylamine) is an antioxidant that is used in the
apple industry to reduce ‘superficial scald’, a chil-
ling injury in apple that, much like bud necrosis, de-
velops in cold storage. In our work, we grew plants
in a continuous 26C greenhouse with intense light
and sprayed them with 100 ppm DPA before cold
storage. We found that DPA reduced bud necrosis
but did not completely inhibit it. Calcium has also
been used to reduce chilling injuries in other crops,
but neither calcium nitrate nor calcium chloride
sprays prevented bud necrosis problem in our trials.
We have not found a better remedy other than alte-
ring cultural or storage practices.
Table 1. Incidence of bud necrosis (% of total buds
showing necrosis) on ‘Mona Lisa’ lilies after 1 week
of cold storage. Plants were grown at 17C and mo-        Fig. 2. Bud necrosis affects many Oriental
ved to various temperature and shade levels one          hybrid lilies such as ‘Mona Lisa’.
week before cold storage (at different temperatures).
Incidence of bud necrosis was calculated based on
the percentage of the number of buds with bud ne-
crosis versus total number of buds used in each
treatment. (Note that values given here do not show
how significant the bud necrosis was).




                                                         Fig. 3. Various stages of bud necrosis on ‘Mona Lisa’
                                                         buds. Top, left to right: No necrotic lesions (0%) to
                                                         40% necrosis along the tepal. Bottom, left to right: 50
                                                         to 100% necrosis along the length of the bud. Any
                                                         rating greater than 2 (necrotic area longer than 1 cm
                                                         around the tepal fringe; middle bud on the top) is
                                                         noticeable and considered unmarketable.
                                                                                 Research Newsletter July 2007 pagina 3
                                                                      0% shade cloth         25% shade cloth          85% shade cloth
                                                                       at 26C ! 3C             at 26C ! 3C              at 26C ! 3C




Fig. 4. The three buds indicated with the bracket are
particularly susceptible during cold storage. These buds
are actively growing at the time of cold storage and
sudden temperature drop in cold storage can induce
severe bud necrosis.


 26C ! 3C                26C ! 7C for                  26C ! 7C
                          2days! 3C


85% shade cloth
at 26C ! 3C
25% shade cloth
at 26C ! 3C
0% shade cloth
at 26C ! 3C

                                                                       Fig. 6. Using heavy shade cloth (85%) can greatly reduce
                                                                       bud necrosis in ‘Mona Lisa’ lilies. All of the plants were
                                                                       grown at 26C and moved directly to 3C cold storage. Top,
 Fig. 6. Using heavy shade cloth (85%) can greatly                     left to right: grown in full sun (control), under 55% shade
reduce bud necrosis in ‘Mona Lisa’ lilies. All of the                  cloth, or 85% shade cloth for a week before cold storage.
plants were grown at 26C and moved directly to 3C                      Bottom: Close-up of the upper part of the plants. Left,
                                                                       grown in full sun (control); right, 85% shade cloth for a
cold storage. Top, left to right: grown in full sun                    week before cold storage.
(control), under 55% shade cloth, or 85% shade
cloth for a week before cold storage. Bottom: Clo-
se-up of the upper part of the plants. Left, grown in
full sun (control); right, 85% shade cloth for a week
before cold storage.
                                                                       Address:                         Address:
                                                                       Dept. of Horticulture            Anthos
                                                                       Cornell University               Weeresteinstraat 12
                                                                       134 Plant Science Building       P.O Box 170
Fig. 5. Two days acclimatization at 7C can reduce bud necrosis         Ithaca, NY 14853                 2180 AD Hillegom
in ‘Mona Lisa’ lilies. All plants grown at 26C in the greenhouse.      USA                              Phone: +31 252 53 50 80
Top, left to right: held at 3C cold storage (control), acclimatized    Phone: + 1 0016072272780:        Fax: +31 252 53 50 88
at 7C for 2 days before moving to 3C, or held at 7C. The
                                                                       Fax: + 1 0016072559998:          secretariaat@anthos.org
acclimatization (7C to 3C) and warmer (7C) storage treatments
greatly reduced bud necrosis. Storage at 7C, however, allowed          wbm8@cornell.edu
further growth of the buds, resulting in unwanted flowering           The newsletter is distributed in North America bij the North
during cold storage. Bottom: Close-up of the upper part of the        American Flowerbulb Wholesalers’ Assn, 2424 Hwy 72/221
plants. Left, held at 3C cold storage (control); right,               E, Greenwood, SC 29666, email: nafwa1@aol.com.
acclimatized at 7C for 2 days before moving to 3C.

                                                                                                 Research Newsletter July 2007 pagina 4

				
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